It is known to produce metal work pieces by the deposition of a weld material onto a base plate. The weld material can be deposited by any one of a number of techniques including laser welding, electron beam welding, metal inert gas welding (MIG) or tungsten inert gas welding (TIG). In MIG or TIG welding a welding torch is provided adjacent a base plate on which the work piece is to be produced. An electrode is provided within the weld torch such that when an electric current is passed therethrough an arc is formed between the weld torch electrode and the base plate. The arc generates heat allowing the welding to take place.
In the MIG process the electrode melts and forms a weld pool in the surface of the work piece. However in TIG welding the arc melts the material of the base plate and a consumable welding wire is fed into the weld pool to form the work piece.
The MIG and TIG welding processes have been used for building up features on conventionally manufactured components. However drawbacks have been encountered in producing such hybrid structures. For example the substrate on which the weld material is deposited must be elevated in temperature to prevent excessive or uneven heat-flow, to help establish process uniformity. This is currently achieved by either heating the substrate with the arc prior to depositing any material or by external heating. Also during the metal deposition process residual forces are generated which have to be relieved by heat treatment.
During the heat treatment process the deposited features are clamped in a fixture to ensure they keep their true shape. However if the deposited feature is manufactured from titanium then the temperature at which it is heat-treated is above the limits for softening the fixture. Using existing fixtures through a thermal cycle for heat-treating titanium severely limits the life of the fixture and the fixtures become expensive consumables.